DelayTruth: Delay setting true variable. TimeoutTruth: Set true to false after timeout

delay_truth.h

#include <chrono>

/*
 * Delay setting true variable
 * test code:
      DelayTruth state(2000);
      EXPECT_FALSE(state);
      state.mark(true);
      EXPECT_FALSE(state);
      sleep(1);
      EXPECT_FALSE(state);
      sleep(2);
      EXPECT_TRUE(state);

      state.mark(false);
      EXPECT_FALSE(state);

      state.mark(true);
      state.mark(false);
      EXPECT_FALSE(state);
      sleep(3);
      EXPECT_FALSE(state);
 */
class DelayTruth {
 public:
  explicit DelayTruth(unsigned delay_ms) : delay_ms_(delay_ms), mark_true_timestamp_(std::chrono::steady_clock::time_point::min()) {}

  auto mark(bool value = true) -> decltype(*this) {
    if (value) {
      mark_true_timestamp_ = std::chrono::steady_clock::now();
    } else {
      // reset the timestamp to mark false
      mark_true_timestamp_ = std::chrono::steady_clock::time_point::min();
    }
    return *this;
  }

  explicit operator bool() const {
    // if the timestamp is min, then it is false
    if (mark_true_timestamp_ == std::chrono::steady_clock::time_point::min()) {
      return false;
    }

    auto diff = std::chrono::steady_clock::now() - mark_true_timestamp_;

    // After the timeout period, it is true
    return diff > delay_ms_;
  }

 private:
  const std::chrono::milliseconds delay_ms_;
  std::chrono::steady_clock::time_point mark_true_timestamp_;
};

timeout_truth.h

#include <chrono>

/*
 * Set true to false after timeout
 * test code:
      TimeoutTruth state(2000);
      EXPECT_FALSE(state);
      state.mark(true);
      EXPECT_TRUE(state);
      sleep(1);
      EXPECT_TRUE(state);
      sleep(2);
      EXPECT_FALSE(state);

      state.mark(false);
      EXPECT_FALSE(state);

      state.mark(true);
      state.mark(false);
      EXPECT_FALSE(state);
      sleep(3);
      EXPECT_FALSE(state);
 */
class TimeoutTruth {
 public:
  explicit TimeoutTruth(unsigned timeout_ms) : timeout_ms_(timeout_ms), mark_true_timestamp_(std::chrono::steady_clock::time_point::min()) {}

  auto mark(bool value = true) -> decltype(*this) {
    if (value) {
      mark_true_timestamp_ = std::chrono::steady_clock::now();
    } else {
      // reset the timestamp to mark false
      mark_true_timestamp_ = std::chrono::steady_clock::time_point::min();
    }
    return *this;
  }

  explicit operator bool() const {
    // if the timestamp is min, then it is false
    if (mark_true_timestamp_ == std::chrono::steady_clock::time_point::min()) {
      return false;
    }

    auto diff = std::chrono::steady_clock::now() - mark_true_timestamp_;

    // if the time difference is greater than the timeout, then the value is false
    return diff < timeout_ms_;
  }

 private:
  const std::chrono::milliseconds timeout_ms_;
  std::chrono::steady_clock::time_point mark_true_timestamp_;
};